HIDING DATA IN COLOR HALFTONE IMAGES USING DOT DIFFUSION WITH NONLINEAR THRESOLDING Volume 2, 15-20 April 2007 April 2007 page(s):Ⅱ-205-Ⅱ-208 Digital Object Identifier 10.1109/ICASSP.2007.366208 Omid Taheri, Ahmad Movahedian Attar, ECE Department, Isfahan University of Technology,Isfahan, Iran Mohammad Mahdi DaneshPanah, ECE Department, University of Connecticut, Storrs CT, USA Reporter:趙旻玥 DATE:June.9.2008

OUTLINE 1 Introduction 2 Dot diffusion halftoning method 3 DDNT algorithm for black and white halftone images 4 Generalizing the DDNT algorithm to color halftone images 5 Simulation results 6 Conclusions

1 Introduction To embed hidden data in halftone images DDNT: dot diffusion with nonlinear thresholding CDDNT: DDNT’s modification to color halftone images Main advantage: the hidden pattern’s intesity can be adjusted by three parameters.

2 Dot Diffusion Halftoning Method For a fixed k: the halftone pixels: A class matrix C:M×N the error: Neighbors with higher class numbers are replaced with: Obtained by parabolic weighting function

3 Dot Diffusion with Nonlinear Thresholding WDD(i,j) and e(i,j) X: the original gray-level image H: the hidden binary image TDD: the halftoned image obtained by traditional dot diffusion method WDD: the watermarked halftone image obtained by DDNT algorithm 1 2 3

4 Generalizing DDNT to Color Halfton Images The dot diffusion must be generalized bo perform on color images: C=[CR CG CB] The halftone version of C: The halftoning process: Three parameters: Mu, Ml, N

5 Simulation Result

6 Conclusions The intensity of the extracted pattern can be adjusted by three variable parameters in the algorithm. The visual qualith of the watermarked image is very good and the hidden pattern can be extracted by overlaying the original and watermarked images as well as by a simple XNOR operation.